What is Kubernetes Cluster Autoscaler?

Question

Accepted Answer

**Cluster Autoscaler** — automatically adjusts node count based on pending Pods.

```yaml
# AWS example
apiVersion: apps/v1
kind: Deployment
metadata:
  name: cluster-autoscaler
  namespace: kube-system
spec:
  template:
    spec:
      containers:
      - name: cluster-autoscaler
        image: registry.k8s.io/autoscaling/cluster-autoscaler:v1.28.0
        command:
        - ./cluster-autoscaler
        - --cloud-provider=aws
        - --nodes=2:10:my-node-group
        - --scale-down-delay-after-add=10m
        - --scale-down-unneeded-time=10m
```

**Behavior:**
- Scales up: pending Pods that can't be scheduled.
- Scales down: nodes with low utilization for 10+ min.
- Respects PDBs and pod disruption budgets.

**Providers:**
- AWS: Cluster Autoscaler or Karpenter.
- GCP: Cluster Autoscaler.
- Azure: Cluster Autoscaler or Node Auto Provisioning.

DevOps: What is Kubernetes Cluster Autoscaler?